1 files changed, 4 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
index ce2a1737f9..415a0576c4 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
@@ -711,6 +711,10 @@ module ActiveRecord
         def add_timestamps_for_alter(table_name, options = {})
           options[:null] = false if options[:null].nil?
 
+          if !options.key?(:precision) && supports_datetime_with_precision?
+            options[:precision] = 6
+          end
+
           [add_column_for_alter(table_name, :created_at, :datetime, options), add_column_for_alter(table_name, :updated_at, :datetime, options)]
         end